Transcript THE OPEN OCEAN

Nervous System and
Sense Organs =
Ch 49
Neuron Structure
• Also known as a nerve cell
• Made of cell body, dendrites and axon
• Dendrite – receives action potentials (many), extend
from cell body
• Axon (one) transmits action potential away from cell
body
Neuron Structure
Neuron Structure
• Electrical signals
transmitted away
from cell body =
action potential
• Axon covered in
lipid layer =
myelin sheath
– Insulates neuron
so it speeds up
rate of
transmission
Nerve Impulse
• Based on membrane potential
(difference in electrical charge) across
cell membrane
• Membrane potential changes w/ + or –
ions (Na and K)
Resting Potential
• Charge across membrane that exists when the
neuron is not conducting action potential
• Neg. charged proteins greater in cell
• K+ ion conc. Is greater inside cell
• Na+ ions greater outside cell
• K+ readily diffuse out of cell leaving the cell
negatively charged (-70 mV)
Action Potential
• Happens when cell is stimulated
• Starts at point where cell body joins axon
• Na+ rush in & Na+ channels open
• Cell becomes more positive than outside
• Outside becomes more neg. than before
• Reverses “polarity” of the cell/environment
Action Potential
• Moves like a wave down length of axon – away
from cell body
• Afterward channels open, Na+ and K+ go back
to “resting” state
• Cannot “fire” again until resting state is
reached
• Requires a lot of ATP
Neurotransmitters
• A synapse is the area where neurons
communicate…junction is called synaptic cleft
• Released at end of axon across synaptic cleft
(space between axon of one and dendrite of
another)
• Go toward receptors on another neuron
causing opening of Na+ channels
• If enough channels open the action potential
starts and will continue to fire, if not, then the
nervous signal is stopped (is inhibited)
Neurotransmitters
Organization
–
Gray matter = cell bodies
–
White matter = axons
1.
Central Nervous System: brain + spinal
cord
2.
Peripheral Nervous System: not brain
or spinal cord
–
Afferent neurons – from nerves in
sense organs toward CNS
–
Efferent neurons – away from CNS
to organs & glands
–
Interneurons btwn motor & sensory
neurons
Brain Structure
Cerebrum
• Largest Portion
• Folded outer layer = cerebral cortex
– Gray matter
• 2 hemispheres for motor & sensory activities
• Voluntary activity
• Cerebral cortex used for:
-higher mental functions, general movement, organ
function, perception and behavioral reactions
-split into the 4 lobes
Cerebellum
• Back of skull
• Coordinates muscle action
• Movement, balance, posture
• Receives sensory impulses
from muscles, tendons,
joints, eyes, ears etc.
Spinal Cord
• Column of nerve tissue
• Spinal nerves originate here
• Sensory (afferent) neurons
carry signals from receptors
to spinal cord through dorsal
roots
• Motor (efferent) neurons
carry signals from spinal
cord to muscles and glands
through ventral roots
Protection
• Skull and vertebrae
• Protective layers (meninges)
• Cerebrospinal fluid
Peripheral Nervous System
• Divided into sensory & motor divisions
• Important For reflexes
• Sensory division: gets info from internal and
external environments
• Motor Division- reaction to sensory info
– Somatic nervous system
– Autonomic Nervous System
Somatic Nervous System
• Control movement of skeletal muscles using
neurotransmitter (acetylcholine)
• Also can be automatic = maintain balance
• Controls reflexes (involuntary & often
protective movements)
– Patellar reflex: ex. Of spinal reflex  bypasses
brain = super fast
Autonomic Nervous System
• Nerves that control internal conditions –
respiration, heartbeat, blood vessels etc.
• Divided into
– parasympathetic- used during normal conditions
– sympathetic division – used in physical or emotional
stress “fight or flight” response
Physiological Effects of the
Autonomic Nervous System
Perception of Stimuli
• Types of Receptors – respond to…..
– Mechano – movement, pressure
– Photo – light
– Chemo – chemicals
– Thermo – temp.
– Pain – tissue damage
Types of Sensory
Receptors
Perception of Stimuli
• Sensory receptors in higher conc. in
sense organs than other body parts
• Turn stimulus into electrical signals that
are sent to brain
Hearing & Balance
• Ear
– detects sound &
– maintains balance
• Sound vibrations directed into ear by “outer
ear”
• Balance: fluid filled semicircular canals and
small hairs using mechanoreceptors
– Bending of hairs releases neurotransmitters
Hearing & Balance
•
Vision
Eyes detect light & transmit signals to brain
• Retina receives the image & transmits through optic
nerve to brain
• rods & cones (photoreceptors) in retina convert
light to electrical signals brain can interpret
– Rods respond dim light
– Cones respond bright light & distinguish color
Structure of the Eye
• Taste
– Chemicals from food enter taste
bud (chemoreceptor)
• Smell
– Olfactory receptors
in epithelium of
nasal passage (chemoreceptor)
Read info about
Drugs, but it
Is not on the test!
Endocrine System = Ch 50
Types of Glands
• Exocrine
– Secrete non hormonal chemicals into
ducts
– Ex: sweat, digestive, salivary, mucous
glands
• Endocrine
– Ductless, secrete hormones into
bloodstream or fluid around cells
Functions of Hormones
– Regulate growth, development, behavior &
reproduction
•
Types
of
Hormones
Hormones: chemicals secreted by cells to influence the activity
of other cells
• Amino Acid Based or are Steroid/Thyroid Hormones…review in
text for RG
Amino Acid-Based Hormones
Steroid & Thyroid Hormones
– Lipids – can pass through target cell memb
– Bind directly to receptor site in cytoplasm or
nucleus
Other Types of Hormones
• Both act “locally”
• Prostaglandins
– Produced by many cells rather than endocrine glands
– Smooth muscles that line air passages, blood
vessels, intestines
– Accumulate in injured areas
• Neuropeptides
– Secreted by nervous system
– Ex: endorphins
Hypothalamus & Pituitary Gland
• Hypothalamus + pituitary gland
= primary regulators of
endocrine system
• Control release of many other
hormones
• Hypothalamus releases
hormones that stimulate or
inhibit release of hormones
from pituitary gland= temp
control
• Pituitary = Growth Hormone
Upper Brain Stem
• Links cerebrum w/ spinal
cord
• Hypothalamus – hunger,
fatigue, anger, body temp.
homeostasis – hormone
control
• Thalamus: relays sensory
info to cerebral cortex
Hormones Secreted by Pituitary
Gland
Thyroid Gland
• Near lower part of larynx
• Metabolism
• Heart rate, blood pressure, temp.,
metabolic rates
Thyroid Gland
• Hyperthyroidism: overproduction of
thyroid hormones, overactivity, high
blood press., body temp
• Hypothyroidism: lethargy, weight gain,
low heart rate
– Caused by iodine deficiency = goiter
Adrenal Glands
• Above each kidney
– Epinephrine &
norepinephrine: nervous
system reaction “fight or
flight”
– Cause liver to produce
glucose  increased
heart rate, pupils dilate,
bronchial tubes enlarge
Gonads
•
•
•
•
Ovaries/Testes
Produce steroid sex hormones
Estrogen/progesterone from ovaries
Testosterone
Pancreas
• Both exocrine & endocrine cells
• Endocrine
– Islets of Langerhans
– Insulin: absorption of glucose in cells (lowers
blood sugar)
– Glucagon: liver releases glucose (increases blood
sugar)
• Type I diabetes, immune cells attack islet
cells & require insulin injections
• Type II diabetes: occurs after age 40, obesity,
poor diet/exercise
Other Endocrine Glands
• Thymus
– Beneath sternum, between
lungs, formation of T-cells
• Pineal
– Near base of brain, melatonin 
sleep patterns
• Parathyroid
– In back of thyroid, increase
concentration of calcium ions in
blood for bone growth & muscle
activity
• Digestive organs
– Stomach  Gastrin
– Small intestine  secretin
Homeostasis
– Stable internal environment
– Antagonistic hormones: opposite effect
• Glucagon/insulin
– Negative Feedback: initial hormone stimulates
other hormones that inhibit release of initial
hormone – has stabilizing effect
– Positive Feedback: initial hormone stimulates
other hormones that stimulate further release of
initial hormone
Negative Feedback Mechanisms